Wales coach Warren Gatland has labelled flanker Dan Lydiate as the "unsung hero" of his Grand Slam-chasing side ahead of their pivotal Six Nations clash with France on Saturday.

Lydiate's prodigious tackle count, physical presence and often unheralded work in many other areas makes him a player Wales cannot do without according to Gatland whose side are chasing their third clean sweep in eight seasons. And the back-row battle between Lydiate, Sam Warburton and Toby Faletau opposite Les Bleus' breakaway trio of Thierry Dusautoir, Julien Bonnaire and Imanol Harinordoquy could prove the game's significant contest.

"Dan is a definitely an unsung hero," Gatland said. "There is not a lot flashy about him. He does a lot of the donkey work to make the others look good and you need those type of people. "They are the glue that holds everything together. He is probably a little bit in the same mould that Richard Hill was with England when England were going so well. People used to say how important he was to the team. Dan is a great athlete, a great professional, and he is important for us."

Skipper Warburton echoed Gatland's sentiments, adding: "I think if you asked anybody in the squad who they thought the three most important players were, I think Dan would come up in a lot of the answers. He is thought of very highly among the players. He is one of our form players, definitely an unsung hero and a key man in this campaign. His work in defence is second to none."

Gatland, meanwhile, believes France will aim to get physical with Wales tomorrow. France coach Philippe Saint-Andre saw his team's Six Nations title and Grand Slam hopes evaporate with a home defeat against England last weekend. And the former Gloucester and Sale Sharks boss has responded by making five changes, plus a positional switch to the wing for prolific try-scoring centre Wesley Fofana.

But they are eminently capable of spoiling the planned Welsh party, given that their Six Nations record in Cardiff shows five wins and one defeat. "I think they are going to come and be very physical with us," Gatland added. "They've picked a tough pack, so we are going to have to expect that real physical contribution they are capable of bringing. It is going to be tough up front.

"Having coached against Philippe in the past in the Premiership, he is relatively conservative in the way he approaches the game. He is very pragmatic in terms of set-pieces and big physical players. I don't think he will care too much about what type of rugby they play, his whole focus is trying to win the match."